Re: [PATCH] md/raid456:Remove the judgement atomic_read(&rdev->read_errors).

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On Wed, 23 May 2012 20:38:16 +0800 "majianpeng" <majianpeng@xxxxxxxxx> wrote:

> It isn't necessary to judge.Because the atomic_read and atomic_set is excuce same cpu. So
> read_errors is zero or not, directly set it zero.

'read' imposes less bus contention than 'write'.  And read_errors will most
often be 0.  So if we can avoid lots of unnecessary writes we should.

i.e. code is correct as it is.

Thanks,
NeilBrown


> Signed-off-by: majianpeng <majianpeng@xxxxxxxxx>
> ---
>  drivers/md/raid5.c |    3 +--
>  1 files changed, 1 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index f351422..1fe2def 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -1690,8 +1690,7 @@ static void raid5_end_read_request(struct bio * bi, int error)
>  			clear_bit(R5_ReadError, &sh->dev[i].flags);
>  			clear_bit(R5_ReWrite, &sh->dev[i].flags);
>  		}
> -		if (atomic_read(&rdev->read_errors))
> -			atomic_set(&rdev->read_errors, 0);
> +		atomic_set(&rdev->read_errors, 0);
>  	} else {
>  		const char *bdn = bdevname(rdev->bdev, b);
>  		int retry = 0;

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